二氧化碳化學吸收程序之動態模擬與控制研究

Dynamic simulation and control of carbon dioxide capture system using chemical absorption

沈明典(Ming-Tien Shen)

指導教授 ： 張煖

淡江大學/工學院/化學工程與材料工程學系碩士班/碩士(2018年)

https://doi.org/10.6846/TKU.2018.00839

摘要

在可見之未來，化石燃料發電仍將是能源供應之最主要方式，其二氧化碳捕捉是面對溫室效應必須採行之作法。醇胺化學吸收程序是處理燃燒後二氧化碳的最可行技術，然而面臨的主要障礙是其高能耗，除了研究的吸收溶劑之外，必須藉由節能流程設計、最佳操作條件與有效控制系統，以使該技術能夠應用於二氧化碳之捕捉。雖然Aspen Plus已有成熟之穩態嚴謹速率模式可以考量分離塔之化學解離與反應，以及熱質傳，然而，至今仍欠缺動態速率模式，以探討二氧化碳化學吸收程序之動態操作特性與控制系統性能。
本研究針對一個300MW燃煤電廠煙道氣之二氧化碳化學吸收程序，利用程序模擬軟體Aspen Custom Model®(ACM)完成了二氧化碳乙醇胺化學吸收程序之動態速率模式建立與驗證。使用30wt% MEA並以90%吸收效率為目標，探討了基本流程與節能流程的設計與穩態最佳化分析，以最低再沸器熱負荷為目標函數，繼而提出利用穩態最佳解為設定點之最佳化控制策略，提出多種控制架構，與傳統控制架構進行控制性能之比較。
以NTNU試驗場數據進行驗證，穩態與動態模擬結果均與實驗值相當吻合。穩態最佳化分析，以最低能耗為目標得到基本流程與節能流程之單位捕獲能耗分別為4.09與3.92 GJ/ton CO2。
基本流程採最佳化控制各種控制架構的控制性能分析結果顯示LG-TStr為最佳之控制架構。相較於CC-TStr傳統控制，LG-TStr 達最終穩態所需時間較傳統控制減少約6小時，安定期之二氧化碳排放量可減少62%，安定期能耗可減少66%。節能流程採最佳化控制各種控制架構的控制性能分析結果顯示LG-LL-TIC為最佳之控制架構。相較於CC-TStr-TIC傳統控制，LG-LL-TIC 達最終穩態所需時間較傳統控制減少約3.5 小時，安定期之二氧化碳排放量無法獲得減少，安定期能耗可減少66%。

關鍵字

碳捕捉 ； 二氧化碳 ； 化學吸收 ； 動態速率模式 ； 控制 ； 最佳化

並列摘要

Fossil fuel power generation will still be major energy supply method, hence the carbon capture for power plant flue gas is essential for the control of global warming. Chemical absorption using amine solvents has been identified as the most feasible technology for post-combustion carbon capture. However, the high energy consumption is still a major problem and requires the development of high-efficient solvents, energy-saving flowsheets, optimal operation conditions and effective process control.
Although rigorous steady-state rate-based models are available in commercial process simulation software, no rigorous dynamic rate-based model is provided in the most popular process simulation software Aspen. In this study, for a 300 MW coal-fired power plant, a dynamic rate-based model for the overall amine-based absorption processes has been developed on the Aspen Custom Modeler platform and verified using literature reported pilot plant data. The model was further utilized for steady state optimization of the standard flowsheet as well as an energy-saving alternative flowsheet, i.e. the inter-cooling absorption process. Several optimal-based control schemes were proposed and compared to the conventional control scheme for the control performance.
For both steady state and dynamic operations, the model simulation results were in good agreement with the NTNU pilot plant data. The minimum reboiler-duty optimization study gives the unit energy consumption results of 4.09 and 3.92 GJ/ton CO2 for the standard and energy-saving processes, respectively.
For the standard a processes, the best control scheme is LG-TStr. Compared to the conventional control scheme, CC-TStr, the stabilization period CO2 emission and reboiler-duty can be reduced by 62% and 66%, respectively. For the energy-saving processes, the best control scheme is LG-LL-TIC. Compared to the conventional control scheme, CC-TStr- TIC, the stabilization period CO2 emission is not reduced, but the reboiler-duty can be reduced by 66%.

並列關鍵字

Carbon capture ； Carbon dioxide ； Chemical absorption ； Rate-based dynamic model ； Control ； Optimization

參考文獻

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